Thermo-responsive hydrogels with tunable transition temperature crosslinked by multifunctional graphene oxide nanosheets

Hydrogels consisting of reactive monomers can respond to external stimuli, which is promising for many applications such as sensors, soft robotics, and actuators, etc. However, most of responsive hydrogels are hard to fabricate into smart devices due to their poor mechanical properties. In this paper, vinyl-modified graphene oxide (GO-VTES) nanosheets were facilely prepared through the coupling reaction between hydroxyl or carboxylic acid groups from graphene oxide (GO) and hydroxyl groups from hydrolyzed vinyltriethoxysilane (VTES). By using the multifunctional GO-VTES nanosheets as crosslinkers, N-iso-propylacrylamide (NIPAM) and acrylamide (AAm) were copolymerized to generate a series of tough and thermo-responsive composite hydrogels. The structures and morphologies of GO-VTES were investigated by FTIR, Raman, XPS, XRD, AFM and TEM. The obtained thermo-responsive composite hydrogels exhibit enhanced mechanical properties, which can be tuned by varying the content of GO-VTES and AAm. Moreover, these hydrogels were thermo-responsive with the LCST tunable by manipulating the contents of GO-VTES and/or AAm in the hydrogels. This strategy to prepare responsive composite hydrogels with enhanced mechanical properties has attractive applications for fabricating smart soft actuators. (C) 2017 Elsevier Ltd. All rights reserved.